she starts fine and runs fine
but the temp gauge only comes up just into white
when i remove water filler cap water over flows
could this be a faulty thermostat sender or is it the head gasket

 

Don't remove the filler cap, the system are under pressure. The boiling point of the water will be higher if the system is under pressure. When you remove it, the pressure will drop and the water will instantly boil.

 

As mentioned they run a pressurised system. Is the fan kicking in at all? Could be a possible dodgy temp sender or a thermostat problem.

 

sounds to me like the fan switch is not functioning! get a hair clip or somthing like it and pull off the plug that goes to switch stick the hair clip in the two terminals so that you are by passing the switch to run parallell! if the motor kicks in then the fans ok and you ,just need a new switch!
If however nothing happens then there could be a fault with the fan